Facilitating effects of berberine on rat pancreatic islets through modulating hepatic nuclear factor 4 alpha expression and glucokinase activity.
OBJECTIVE
To observe the effect of berberine on insulin secretion in rat pancreatic islets and to explore its possible molecular mechanism.


METHODS
Primary rat islets were isolated from male Sprague-Dawley rats by collagenase digestion and treated with different concentrations (1, 3, 10 and 30 micromol/L) of berberine or 1 micromol/L Glibenclamide (GB) for 24 h. Glucose-stimulated insulin secretion (GSIS) assay was conducted and insulin was determined by radioimmunoassay. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was performed to evaluate cytotoxicity. The mRNA level of hepatic nuclear factor 4 alpha (HNF4alpha) was determined by reverse transcription polymerase chain reaction (RT-PCR). Indirect immunofluorescence staining and Western blot analysis were employed to detect protein expression of HNF4alpha in the islets. Glucokinase (GK) activity was measured by spectrophotometric method.


RESULTS
Berberine enhanced GSIS rather than basal insulin secretion dose-dependently in rat islets and showed no significant cytotoxicity on islet cells at the concentration of 10 mumol/L. Both mRNA and protein expressions of HNF4alpha were up-regulated by berberine in a dose-dependent manner, and GK activity was also increased accordingly. However, GB demonstrated no regulatory effects on HNF4alpha expression or GK activity.


CONCLUSIONS
Berberine can enhance GSIS in rat islets, and probably exerts the insulinotropic effect via a pathway involving HNF4alpha and GK, which is distinct from sulphonylureas (SUs).
Wang
Zhi-Quan
ZQ
Huazhong University of Science and Technology, Wuhan 430030, Hubei Province, China.
Lu
Fu-Er
FE
Leng
San-Hua
SH
Fang
Xin-Sheng
XS
Chen
Guang
G
Wang
Zeng-Si
ZS
Dong
Li-Ping
LP
Yan
Zhong-Qing
ZQ
D000818:Animals; D001599:Berberine / Q000494:pharmacology*; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D005941:Glucokinase / Q000378:metabolism*; D005947:Glucose / Q000494:pharmacology; D005905:Glyburide / Q000494:pharmacology; D051557:Hepatocyte Nuclear Factor 4 / Q000378:metabolism*; D007004:Hypoglycemic Agents / Q000494:pharmacology; D007328:Insulin / Q000378:metabolism; D007515:Islets of Langerhans / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D010936:Plant Extracts / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley
D051557:Hepatocyte Nuclear Factor 4; C496594:Hnf4a protein, rat; D007004:Hypoglycemic Agents; D007328:Insulin; D010936:Plant Extracts; D001599:Berberine; D005941:Glucokinase; D005947:Glucose; D005905:Glyburide